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(CNN) - The FBI said Monday it believes it knows who was behind one of the most significant art heists in the United States - the 1990 theft of 13 precious works, once valued at $500 million, from Boston's Isabella Stewart Gardner Museum.

A couple of catches in the announcement: The FBI didn't reveal the suspects' names, and the artwork still hasn't been recovered. But the FBI said the suspects "are members of a criminal organization with a base in the mid-Atlantic states and New England."FULL POST